Changes In Population Density Research Articles

Complex Dynamics of a Discrete-Time Food Chain Model

In a food chain, the role of intake patterns of predators is very influential on the survival and extinction of the interacting species as well as the entire dynamics of the ecological system. In this study, we investigate the affluent and intricate dynamics of a simple three-species food chain model in a discrete-time framework by analyzing the parameter plane of the system with simultaneous changes of two crucial parameters, the predation rates of middle and top predators. From the theoretical viewpoint, we study the model by determining the fixed points’ biological feasibility and local asymptotic stability criteria, and performing some analyses of local bifurcations, namely, transcritical, flip, and Neimark–Sacker bifurcations. Here, we initiate the numerical simulation by plotting the changes of the prey population density in terms of a vital parameter of the system, and we observe the switching among different dynamical behaviors of the system. We also draw some phase portraits and plot the time series solutions to show the diverse characteristics of the system dynamics. Further, we move one step ahead to explore the intricate dynamical scenarios appearing in the parameter plane by forming Lyapunov exponent and isoperiodic diagrams. In the parameter plane of the system, we see the emergence of innumerable Arnold tongues. All these Arnold tongues are organized along a particular direction, and the beautiful arrangement of these tongues forms several kinds of period-adding sequences. The study sheds more light on various types of multistability occurring in the model system. We see the coexistence of three periodic attractors in the parameter plane. In this study, the most striking observation is the coexistence of four periodic attractors, which occurs infrequently in ecological systems. We draw the basins of attraction for the tristable and tetrastable attractors, which are complex Wada basins. A system with Wada basin is very sensitive to initial conditions and more erratic in nature than a system with fractal basin. Also, we plot the density of all interacting species in terms of the predation rates of middle and top predators and observe the variation in the population densities of all species with the variability of these two key parameters. In the parameter plane created by the simultaneous changes of two parameters, the system exhibits a variety of intricate and subtle dynamics, which cannot be found by changing only a single parameter.

DNA metabarcoding as a tool for characterising the spatio-temporal distribution of planktonic larvae in the phylum Echinodermata

AbstractMetabarcoding is revolutionising the analysis of biodiversity in marine ecosystems, especially as it provides a means of detecting and identifying cryptic life stages in field samples. The planktonic larval stage of many species underpins the abundance and distribution of adult populations but is challenging to characterise given the small size of larvae and diffuse distributions in pelagic waters. Yet, planktonic larval dynamics are key to understanding phenomena observed in adult populations, such as the boom-and-bust dynamics exhibited by some echinoderms. Rapid changes in echinoderm population density can have significant effects on local benthic ecosystems. For example, outbreaks of the crown-of-thorns sea star (CoTS) on the Great Barrier Reef (GBR) have led to considerable declines in coral cover. Here, we used a DNA metabarcoding approach to investigate the spatio-temporal distribution and diversity of echinoderm larvae on the GBR, including CoTS. Generalised linear mixed models revealed that echinoderm larval richness, was significantly correlated with temporal variables (i.e. season and year) which is consistent with expected fluctuations in larval output based on adult spawning periodicity. However, neither site-specific differences in echinoderm larval richness, nor correlations between larval composition and environmental, temporal, or spatial variables were found. This study validates the utility of metabarcoding approaches for detecting and characterising echinoderm larvae, including CoTS, which could prove useful to future monitoring efforts. Our findings suggest that metabarcoding can be used to better understand the life history of planktonic larvae, and analyses combining environmental (e.g., temperature, nutrients) and oceanographic (e.g., currents) data could deliver valuable information on the factors influencing their spatio-temporal distributions.

Livelihood adaptation to changes in River Ekulu depth, channel width and riverbank vegetation cover type by household breadwinners in selected communities in Enugu, Nigeria

Nigeria and most other developing countries need to explore using socio-ecological approaches to address some ecosystem challenges. Changes in river depth, channel width and riverbank vegetation cover type of River Ekulu in Enugu, Nigeria, their causes and effects on biodiversity and livelihood adaptation by household breadwinners, who depended on the river for livelihood activities, were investigated. Snowball sampling technique was adopted. Causes of changes in the river depth, channel width and riverbank vegetation cover type and their effects on biodiversity and livelihood adaptation were obtained from literature with Google Forms administered to purposively selected experts. Factor component analysis was used to select the significant ones. Aerial images of the river were captured with a drone. Questionnaire was used to elicit information from the target household breadwinners to corroborate the images or otherwise, the causes and the effects of the changes on biodiversity and livelihood adaptation. Data were analyzed to test seven null hypotheses bordering on the objectives of the study. Results showed that the observed changes led to adverse effect on biodiversity and the attendant imperative livelihood adaptation. Factors causing the changes in the river depth, width and riverbank vegetation cover type were climate change (factor weight, fw, 0.44–0.54) and increase in population density (fw 0.46–0.63). Recommendations include conscientisation of government and riverine neighbourhood dwellers on the observed ecological changes, their causes and effects, and ways-forward on policies and practices.

A computational linguistic methodology for assessing semiotic structure in prehistoric art and the meaning of southern Scandinavian Mesolithic ornamentation

Non-figurative prehistoric art is comparatively common yet challenging to decode and hence to understand. At the heart of the difficulty of assessing the presence of semiotic structure in prehistoric art is a lack of appropriate, replicable, and case-transferable methodologies. We here propose a novel approach derived from computational linguistics, in which k-skip-n-gram (skipgram) models and associated pointwise mutual information (PMI) measures are customised to the analysis of prehistoric art. In applying this methodology to a large corpus of portable art from the South Scandinavian Mesolithic, we demonstrate how the mutual relationship between individual motifs can be established. In the case of Mesolithic portable art, our analysis strongly suggests that there is no evident semiotic structure – this was likely not a form of proto-writing – but salient changes of motif occurrence over time are detectable. These changes are sensitive to changes in population density, structure, and connectedness, and may relate to increased territoriality in the Late Mesolithic. The method presented here is readily case-transferable and renders possible further linguistic and semiotic analyses of prehistoric art.

Spatio-temporal Mapping of Population Density and their Characteristics of the Eastcentral Rajmahal Highlands, Jharkhand, India

Population growth and population density are two important variables for population studies. The study of human resource reveals that population in the Eastcentral Rajmahal Highlands is gradually increasing. The decadal disparity of population growth of the study area shows a positive trend with distinct fluctuations rate of increase. The study area shows the change in population density from 206 persons per sq. km and 381 persons per sq. km in 1971 and 2011 respectively. The co-efficient of correlation between population growth and population density is highly positive relationship. Maximum populations are settled in the rural areas. Only 10.79 % (47,584) of the population are urban. It represents an unbalanced rural-urban population ratio and it also shows that rural economy particularly agriculture is dominating in the study area. The purpose of this paper is to analyse as well as spatial and temporal mapping of population density in the study area.

The sustainability of development pathways and climate change vulnerability in the Americas

Sustainability transformation requires societies to shift their development pathways to maintain ecological integrity and supply basic human needs over generations. We examine the sustainability of the development pathways of 351 national and sub-national geopolitical units in the Americas between 2001 and 2020. Then, we test the hypothesis that such pathways are influenced by land area, population size and topographic heterogeneity. Finally, we combine information about the sustainability of development pathways with population density and future climate change index to identify the Americas' socio-climatic hotspots. The Americas is a mosaic of geopolitical units following distinct development pathways. Most (74.3%) of the geopolitical units have, to date, followed unsustainable development pathways. Altogether, they represent 37.6% of the Americas' land area and are home to 83.3% of the Americas' population. Land area and topographic heterogeneity facilitate sustainable pathways, while population size constrains them. Climate change will affect all geopolitical units, but those with unsustainable development pathways, a high population density and high climate change index are expected to be particularly vulnerable and should be considered priorities for climate-resilient development programmes. There is a need for integrated place-based policies that strengthen ecological and socio-economic infrastructures to advance sustainable development pathways under changing climate conditions.

Exploring patterns of female house mouse spatial organisation among outbreaking and stable populations.

The size and distribution of home ranges reflect how individuals within a population use, defend, and share space and resources, and may thus be an important predictor of population-level dynamics. Eruptive species, such as the house mouse in Australian grain-growing regions, are an ideal species in which to investigate variations in space use and home range overlap between stable and outbreaking populations. In this study, we use spatially explicit capture-recapture models to explore if space use and home range overlap among female mice could serve as indicators of changes in population density leading into summer. Additionally, we assess the sensitivity of space use and home range estimates to reduced recapture rates. Our analysis did not reveal variations in the spring spatial organisation of female mice based on existing capture-mark-recapture data. However, our study highlights the need to balance monitoring efforts within regions, emphasising the importance of exploring studies that can improve spatial recaptures by optimising trapping efforts. This is particularly important in Australian agricultural systems, where varying farm management practices may drive differences in population dynamics.

Analysis of population density and land use in Karangmalang Subdistrict, Sragen Regency in 2013 and 2022

Increased population growth is one of the driving factors for land use change because it is to meet the needs of the population, especially in settlements or residences. Land use changes occur as a result of improving the quality of human life which has an impact on land use changes that are difficult to control. This study aims to analyze the distribution of land use in 2013 and 2022, and analyze the relationship between population density and land use change. The research method used is the Overlay Method and Liner Regression. The results of this study show that land use change in Karangmalang Subdistrict in 2013 and 2022 amounted to 197.7 hectares, dominated by residential land of 154.4 hectares. There was an increase in population in 2013 and 2022 of 2,280 people/square kilometer. The results of the linear regression calculation show an R2 value of 0.697 which means that there is a positive relationship between land use change and an increase in population density.

Motion‐sensitive cameras track population abundance changes in a boreal mammal community in southwestern Yukon, Canada

AbstractMotion‐sensitive cameras are commonly used to monitor wildlife occupancy rates; however, few studies have assessed whether data from cameras are correlated with density estimates obtained from more traditional labor‐intensive methods such as those based on capture‐mark‐recapture. We used data from a boreal forest community to test whether camera data were correlated with densities estimated from independent monitoring methods. We placed 72 covert cameras in the forest around Lhù'ààn Mân' (Kluane Lake), Yukon, Canada, for 7 years and tracked changes in population densities by camera hit rates. We independently estimated population densities of snowshoe hares (Lepus americanus) and red squirrels (Tamiasciurus hudsonicus) using capture‐mark‐recapture via live trapping, and Canada lynx (Lynx canadensis), coyotes (Canis latrans), and moose (Alces americanus) by snow track transects. Density estimates obtained from conventional aerial surveys were also periodically available for moose. Except for red squirrels, camera hit rates were highly correlated with population density estimates obtained by traditional methods, including across a large range of estimated densities corresponding to cyclic population dynamics in several species. Accordingly, we infer that motion‐sensitive cameras could supplement or replace traditional methods for monitoring key species in boreal forest food webs. Using cameras to monitor population change has several advantages; they require less effort in the field, are non‐invasive compared to live‐trapping, include multiple species at the same time, and rely less on weather than either aerial surveys or snow track transects. Tracking changes across the vast boreal forest is becoming increasingly necessary because of climate and landscape change and our data validate the use of motion‐sensitive cameras to provide a useful quantitative method for state‐of‐the‐environment reporting.

Contribution of climate change to the spatial expansion of West Nile virus in Europe

West Nile virus (WNV) is an emerging mosquito-borne pathogen in Europe where it represents a new public health threat. While climate change has been cited as a potential driver of its spatial expansion on the continent, a formal evaluation of this causal relationship is lacking. Here, we investigate the extent to which WNV spatial expansion in Europe can be attributed to climate change while accounting for other direct human influences such as land-use and human population changes. To this end, we trained ecological niche models to predict the risk of local WNV circulation leading to human cases to then unravel the isolated effect of climate change by comparing factual simulations to a counterfactual based on the same environmental changes but a counterfactual climate where long-term trends have been removed. Our findings demonstrate a notable increase in the area ecologically suitable for WNV circulation during the period 1901–2019, whereas this area remains largely unchanged in a no-climate-change counterfactual. We show that the drastic increase in the human population at risk of exposure is partly due to historical changes in population density, but that climate change has also been a critical driver behind the heightened risk of WNV circulation in Europe.

Soybean-mediated suppression of BjaI/BjaR1 quorum sensing in Bradyrhizobium diazoefficiens impacts symbiotic nitrogen fixation.

The acyl-homoserine lactones (AHLs)-mediated LuxI/LuxR quorum sensing (QS) system orchestrates diverse bacterial behaviors in response to changes in population density. The role of the BjaI/BjaR1 QS system in Bradyrhizobium diazoefficiens USDA 110, which shares homology with LuxI/LuxR, remains elusive during symbiotic interaction with soybean. Here this genetic system in wild-type (WT) bacteria residing inside nodules exhibited significantly reduced activity compared to free-living cells, potentially attributed to soybean-mediated suppression. The deletion mutant strain ΔbjaR1 showed significantly enhanced nodulation induction and nitrogen fixation ability. Nevertheless, its ultimate symbiotic outcome (plant dry weight) in soybeans was compromised. Furthermore, comparative analysis of the transcriptome, proteome, and promoter activity revealed that the inactivation of BjaR1 systematically activated and inhibited genomic modules associated with nodulation and nitrogen metabolism. The former appeared to be linked to a significant decrease in the expression of NodD2, a key cell-density-dependent repressor of nodulation genes, while the latter conferred bacterial growth and nitrogen fixation insensitivity to environmental nitrogen. In addition, BjaR1 exerted a positive influence on the transcription of multiple genes involved in a so-called central intermediate metabolism within the nodule. In conclusion, our findings highlight the crucial role of the BjaI/BjaR1 QS circuit in positively regulating bacterial nitrogen metabolism and emphasize the significance of the soybean-mediated suppression of this genetic system for promoting efficient symbiotic nitrogen fixation by B. diazoefficiens.IMPORTANCEThe present study demonstrates, for the first time, that the BjaI/BjaR1 QS system of Bradyrhizobium diazoefficiens has a significant impact on its nodulation and nitrogen fixation capability in soybean by positively regulating NodD2 expression and bacterial nitrogen metabolism. Moreover, it provides novel insights into the importance of suppressing the activity of this QS circuit by the soybean host plant in establishing an efficient mutual relationship between the two symbiotic partners. This research expands our understanding of legumes' role in modulating symbiotic nitrogen fixation through rhizobial QS-mediated metabolic functioning, thereby deepening our comprehension of symbiotic coevolution theory. In addition, these findings may hold great promise for developing quorum quenching technology in agriculture.

Elevated genetic risk for multiple sclerosis emerged in steppe pastoralist populations

Multiple sclerosis (MS) is a neuro-inflammatory and neurodegenerative disease that is most prevalent in Northern Europe. Although it is known that inherited risk for MS is located within or in close proximity to immune-related genes, it is unknown when, where and how this genetic risk originated1. Here, by using a large ancient genome dataset from the Mesolithic period to the Bronze Age2, along with new Medieval and post-Medieval genomes, we show that the genetic risk for MS rose among pastoralists from the Pontic steppe and was brought into Europe by the Yamnaya-related migration approximately 5,000 years ago. We further show that these MS-associated immunogenetic variants underwent positive selection both within the steppe population and later in Europe, probably driven by pathogenic challenges coinciding with changes in diet, lifestyle and population density. This study highlights the critical importance of the Neolithic period and Bronze Age as determinants of modern immune responses and their subsequent effect on the risk of developing MS in a changing environment.

Effect of rabies vaccination on population densities of Vulpes vulpes in south-western Poland (Carnivora: Canidae)

Despite intensive studies on the red fox (Vulpes vulpes), little is known about current spatial and temporal dynamics of red fox populations. This study analysed the spatial and temporal changes of red fox populations in the south-western part of Poland in relation to main factors shaping the changes, above all the rabies vaccination. After a long period of low population density depressed by rabies, a rapid increase took place in the last decade of the 20th century, as a consequence of vaccination applied on a wide scale throughout SW Poland. The populations reached the highest levels ever in the two first decades of the 21st century, they stabilized, and at the end of the second decade they begun to decline. In 2001–2020, the crude population density ranged from 0.6 to 12 red foxes per 100 ha. It was highest in the regions with the lowest afforestation (6.7–12 ind./100 ha), whereas in the regions with the highest afforestation it was the lowest (0.6–0.8 ind./100 ha). The ecological consequences of these changes in the fox population densities are paralleled with changes in population densities of many prey species and fox’s competitors.

People inflows as a pandemic trigger: Evidence from a quasi-experimental study

Although it has been established that population density can contribute to the outbreak of the COVID-19 virus, there is no evidence to suggest that economic activities, which imply a significant change in mobility, played a causal role in the unfolding of the pandemic. In this paper, we exploit the particular situation of Sardinia (Italy) in 2020 to examine how changes in mobility due to tourism inflows (a proxy of economic activities) influenced the development of the COVID-19 pandemic. Using a difference-in-differences approach, we identify a strong causal relationship between tourism flows and the emergence of COVID-19 cases in Sardinia. We estimate the elasticity of COVID-19 cases in relation to the share of tourists to be 4.1%, which increases to 5.1% when excluding local residents. Our analysis suggests that, in the absence of tools preventing the spread of infection, changes in population density due to economic activities trigger the pandemic spreading in previously unaffected locations. This work contributes to the debate on the complex relationship between COVID-19 and the characteristics of locations by providing helpful evidence for risk-prevention policies.

Urban form in India 1975–2015: Have India's cities become flat?

We focus on two questions in this paper. First, are Indian cities suburbanizing or is their growth compact? Second, what explains the differences in suburbanization or compact growth across cities and regions? We answer these questions using granular, grid-level data from the Global Human Settlements Layer.We take three approaches to understanding the evolution of urban form. First, we explain changes in population density based on concentric rings around the city centre for 100 cities in India. Second, we use these same data to estimate population density gradients in 1975 and 2015. Finally, we use regressions to test hypotheses about relationships between city characteristics and the density gradient.We find that although cities in India densified within their 1975 city limits, they also expanded outward. We find the negative exponential density function is useful for studying urban form in India. South Indian cities and those in urbanized states sprawled more than their northern and less urbanized counterparts. Both the social conditions of central cities such as the literacy rate and the historical pattern of population suburbanization are statistically significantly associated with suburbanization. This suggests the need for greater investment in public infrastructure in central cities to support compact urban growth.

Recruitment dynamics in a tropical karst seasonal rain forest: Revealing complex processes from spatial patterns

Spatial patterns can reveal many ecological processes in forest communities; thus, understanding the spatial patterns of trees and their interactions is key to exploring forest dynamics. However, few studies have explored the spatial patterns and interactions between adults and recruits over longer time spans in tropical karst forests. A forest dynamics census was conducted (2011–2021) in a 15-ha karst seasonal rainforest plot at the Nonggang National Nature Reserve, in Guangxi, China. The tree community structure, which included a total of 20 tree species (≥ 50 individuals) at various states of recruitment, survival, and mortality, were selected and investigated via detailed analyses. First, univariate pair correlation functions and bivariate mark correlation functions were utilized to analyze the spatial patterns of dead recruits, surviving recruits, and adults. Aggregation was the dominant intraspecific distribution pattern in the plot that decreased at larger scales, which indicated that dispersal was limited. The segregation of bivariate patterns in most species suggested that there was scramble competition between the surviving and dead recruits, which translated to their not clustering around adults. Second, it was revealed through testing that density dependence was not prevalent. However, negative density dependence was more common in species that exhibited density dependence, as various species respond differently to changes in population density. Third, most recruits had a low probability of survival, which for several dominant species was influenced by neighborhood effects. This study did not support the Janzen-Connell hypothesis, as the survival probability of most recruits was not enhanced with the distance from adults. This meant that the effects of distance from adults on the growth of recruits in Nonggang forests were negligible. These results suggested that dispersal limitations and habitat heterogeneity played more significant roles in the regulation of tree spatial patterns and seedling growth (or mortality) in tropical karst seasonal rain forests. This work will contribute to the restoration and conservation of fragile forest communities in Karst regions, while providing a theoretical basis for biodiversity research, forest management planning, and ecosystem services.

Recycling rate performance and socioeconomic determinants: Evidence from aggregate and regional data across European Union countries

The recycling rates for the EU Member States deviate significantly from the targets set by Directive (2018)/851 for attaining the target of 55% by 2025 (European union, 2018). The aim of the study is to investigate the short- and long-term relationship between macroeconomic variables and the recycling rates performance at both national and regional level. Within this context, four sets of variables are examined, namely sociodemographic, economic and institutional factors. For the purpose of the analysis, the available data acquired from 28 EU countries during the period between 2000 and 2020, as well as from 38 EU regions during 2000–2018 and a panel data approach using OLS, Fixed Effects, Random Effects, FMOLS, and ECM techniques is implemented. Findings robustly indicate that factors such as economic performance, institutional quality, and higher educational attainment significantly contribute to the EU circular economy. Results imply that changes in agricultural intensification and population density significantly affect recycling levels. A particularly significant finding that contributes to the existing literature is the higher speed of adjustment, as indicated by the lagged ECT, at the NUTS-1 level compared to the NUTS-2 level. Thus, recycling policy outcomes, implemented policies, and interventions adjust more rapidly towards their equilibrium state, resulting in immediate impacts and faster changes at NUTS-1 level. On the contrary, it takes more time for these policy outcomes to materialize at the regional scale. Policymakers should prioritize reducing income disparities, improving transparency, investing in education, and promoting sustainable agriculture and waste management infrastructure to support the circular economy.

Cumulative disadvantage during childhood: The association between moving and accumulated neighborhood deprivation over a child’s life course in the Netherlands

ABSTRACT While the importance of residential moves and neighborhood context for children is widely recognized, few studies examine childhood mobility and neighborhood context together and over time. Using a typology of mobility trajectories based on frequency, age, distance and change in population density, this study analyzes the interrelatedness between mobility trajectories and socioeconomic neighborhood composition throughout childhood. Using full-population register data, we follow children born in the Netherlands in 1999 until age 16. Local spatial autocorrelation analyses reveal concentrations of childhood mobility and neighborhood deprivation in cities. Focusing on children born in metropolitan areas, results indicate that children born in deprived neighborhoods are more likely to experience any move. Short-distance moves are associated with increased exposure and long-distance moves with less exposure to neighborhood deprivation. We argue we need a multidimensional longitudinal perspective to fully capture residential contexts to which children are exposed and enhance knowledge of childhood accumulations of disadvantage.

Design and spatial pattern optimization for a sponge city using factor analysis and geographical statistics to restore urban resilience: A case study in a coastal area of China

Abstract The sponge city is a new concept of stormwater management for ecological city construction, which aims to restore water-cycle processes and reduce runoff. Cities in coastal districts are suffering from serious instability due to high population density, urbanization, and land-use changes. However, previous research contains few evaluations of balancing urban ecological indicators of sponge city performance, including geographical, environmental, economic, and social factors, and their effect on resilience at a macro level to develop low-impact development schemes. In this study, we developed an integrated framework using factor analysis, geographical statistics, multi-objective analysis, and remote sensing methods to extract the factors influencing sponge city resilience and to establish spatial pattern schemes. The results indicated that the urbanization degree and plant adaptability had the greatest impact on sponge city performance, with weights of 45 and 27%, respectively. Sponge city spatial pattern schemes performed the best in the combination scenario of 14.8–46.8% green roofs (by area ratio) supported by grooves and rain barrels +10% herbaceous basins divided into units by ecological tree pools +10% permeable pavements and sidewalks. This scenario balanced facilities and cost to optimize the spatial pattern, which improved sponge city adaptability and urban ecological conditions.

A Study on the Drivers of Carbon Emissions in China’s Power Industry Based on an Improved PDA Method

The power industry is a major source of carbon emissions in China. In order to better explore the driving factors of carbon emissions in China’s power industry and assist the Chinese government in formulating emission reduction strategies for the power industry, this study applies the improved production-theoretical decomposition analysis (PDA) method to analyze the carbon emission drivers of China’s power industry. This study investigates the impact of energy intensity, per capita GDP, population density, power generation structure, and environmental climate on carbon emissions in China’s power industry in 30 provinces from 2005 to 2020. It was found that the carbon emission ratios of the power sector in all provinces and cities are basically greater than 1, which indicates that carbon emissions in most of the power sectors in the country are still increasing as of 2020. Overall, the effects of potential thermal fuel carbon emission efficiency, potential thermal energy consumption efficiency, the carbon emission efficiency of thermal power generation, economic scale, population density, and annual rainfall change are mostly greater than 1 and will promote the growth of carbon emissions in the power sector. Moreover, the effects of thermal power generation energy efficiency technology, thermal power generation emission reduction technology, power generation structure, and power generation per unit GDP are mostly less than 1 and will inhibit the growth of carbon emissions in the power sector. However, each of these drivers does not have the same degree of influence and impact effect for each province and city. Based on the research results, some policy recommendations are proposed.